1. Field of the Invention
The present invention relates to a positive electrode active material for a lithium ion battery, a positive electrode for a lithium ion battery, a lithium ion battery, and a method for producing a positive electrode active material for a lithium ion battery.
2. Description of Related Art
A lithium-containing transition metal oxide is generally used as a positive electrode active material of a lithium ion battery. Specifically, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), or the like is used, and the compounding thereof is being advanced in order to improve the performance (achievement of high capacity, cycle characteristics, storage characteristics, reduction of internal resistance, rate properties) and increase the safety. For a lithium ion battery in a large battery usage such as for car installation and load leveling, characteristics different from a conventional lithium ion battery for cell phones and personal computers are in demand.
For the improvement of battery performance, various methods are conventionally used, and for example, Patent document 1 discloses a positive electrode active material for a nonaqueous electrolyte secondary battery containing secondary particles and/or primary particles comprising a plurality of primary particles, having an average number A represented by formula (1) of 1 or more and 10 or less, a specific surface area of 0.20 m2/g or more and less than 0.50 m2/g, and an alkalinity of 25 ml or less,A=(m+p)/(m+s)  (1)    wherein m is the number of primary particles only, p is the number of primary particles constituting secondary particles, and s is the number of secondary particles,    and having a composition represented by the following formula;LixCo1-yMyO2+Z     wherein M is one or more elements selected from Na, Mg, Ca, Y, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, N, P, S, F, and Cl, 0.9≦x≦1.1, 0≦y≦0.1, and −0.1≦z≦0.1. Moreover, it is described that, based on the above, a battery having high load characteristics, excellent quality stability, and high capacity characteristics can be prepared.
In addition, Patent document 2 discloses a nonaqueous secondary battery comprising a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode has a positive electrode mixture containing a lithium-containing complex oxide, a conductive aid, and a binder, the lithium-containing complex oxide is represented by a general formula Li1+x+αNi(1−x-y-δ)/2Mn(1−x-y-δ)/2MyO2 [wherein 0≦x≦0.05, −0.05≦x+α≦0.05, 0≦y≦0.4, and −0.1≦δ0.1, and M is one or more elements selected from the group consisting of Mg, Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn], is a complex oxide in which primary particles agglutinate to form a secondary particle, the average particle size of the primary particles is from 0.8 to 3 μm, the average particle size of the secondary particles is from 5 to 20 μm, is a mixture containing a lithium-containing complex oxide A having a BET specific surface area of from 0.6 to 2 m2/g and a lithium-containing complex oxide B having an average particle size smaller than the average particle size of secondary particles of the complex oxide A, the average particle size of the complex oxide B is ⅗ or less of the average particle size of the secondary particles of the complex oxide A, and the ratio of the complex oxide B is 10 to 40% by weight of the total positive electrode active material. Moreover, it is described that, based on the above, a nonaqueous secondary battery having high capacity, excellent cycle durability, and storage properties under high temperature can be provided.
Furthermore, Patent document 3 discloses that, when a lithium metal complex oxide represented by LiNi1-xMxO2 (wherein M is at least one or more metal elements selected from the group consisting of Co, Al, Mg, Mn, Ti, Fe, Cu, Zn, and Ga, and 0.25>x≧0) is produced, in the production method to obtain a lithium metal complex oxide by mixing a nickel complex oxide obtained by heat-treating a nickel complex hydroxide in which M is dissolved or added, and a lithium compound, and heat-treating, the method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery, wherein a nickel complex hydroxide in which M is previously dissolved or added is heat-treated at a temperature of 650° C. or more and less than 900° C., and a mixture of the obtained nickel complex oxide and a lithium compound is heat-treated at a temperature of 650° C. or more and 850° C. or less, and the heat treatment temperature of the mixture of the nickel complex oxide and a lithium compound is set lower than the heat treatment temperature to obtain the nickel complex oxide. Moreover, it is described that, based on the above, a secondary battery capable of achieving high capacity of battery, improving coulombic efficiency, and reducing irreversible capacity can be provided.    (Patent document 1) Japanese Patent No. 4287901    (Patent document 2) Japanese Patent No. 4070585    (Patent document 3) Japanese Patent No. 3835266